Abstract: A rotatable slotted cylinder (RSC), partially embedded within the contours of a tail surface, such as an aircraft tail airfoil, serves as a force-producing element in a closed-loop active control system for buffet alleviation. A longitudinal axis of the RSC runs spanwise to the airfoil at or near the three-quarter chord location. In a so-called "home" position, the RSC projects as two small spanwise humps out of opposite sides of the tail surface. By active feedback control using a buffet response signal measured by an accelerometer, the RSC rotates up to .+-.45.degree. maximum deflection from the home position, thus allowing free stream air to flow through the airfoil, thereby creating lift forces for the active alleviation of the buffet response on the tail surface. An alternate embodiment of the invention places the RSC and a drive motor assembly outside of and adjacent to the tail surface near the airfoil quarter chord station.

Abstract: Higher harmonic control (hereinafter HHC) of helicopter rotor blade vibrations is provided by an actively controlled, rotatable, slotted cylinder which is mounted at an outboard section of each blade. Continuous rotation of each cylinder about its longitudinal axis produces a periodic aerodynamic force on the blade at a frequency of twice the rotational frequency of the cylinder. The amplitude of force is controlled by the size of a slot opening in the cylinder while the rotational speed of the cylinder is synchronized to run at a multiple of the speed of a rotor blade drive shaft. The amplitude and phase of the HHC force is regulated, either manually or by active feedback control, to minimize any vibratory load transmitted to the airframe through the rotor blade drive shaft. A significant advantage offered by this concept relative to other HHC methods, such as high-frequency blade pitch motions actuated either by the swash plate or by moveable tabs at the blade trailing edge, is its low power requirement.

Abstract: A low frequency torsional suspension system for testing a space structure uses a plurality of suspension stations attached to the space structure along the length thereof in order to suspend the space structure from an overhead support. Each suspension station includes a disk pivotally mounted to the overhead support, and two cables which have upper ends connected to the disk and lower ends connected to the space structure. The two cables define a parallelogram with the center of gravity of the space structure being vertically beneath the pivot axis of the disk. The vertical distance between the points of attachment of the cables to the disk and the pivot axis of the disk is adjusted to lower the frequency of the suspension system to a level which does not interfere with frequency levels of the space structure, thereby enabling accurate measurement.

Abstract: A flutter exciter induces vibration either for actual aircraft flight testing or for wind tunnel model testing. The basic flutter exciter unit is a pair of rotatable concentric cylinders mounted on either a fixed vane or an aircraft wing or a tail surface. Each cylinder has a slot which allows the air flow to pass therethrough. By rotating the cylinders together, oscillating air pressures are induced on the fixed vane or the aircraft surface to which the cylinders are attached. The cylinders may be mounted at a trailing edge of either the fixed vane or the aircraft wing, to any tail surface, or on any other lifting surfaces of the aircraft itself. Thus, because the flutter exciter can be made as a completely self-contained unit, it may be simply mounted to any suitable hard point on either the test model or the aircraft. The power required to rotate the slotted cylinders is minimal, thus allowing the use of a low wattage motor.

Abstract: This is a device for suspending a store 15 from a support such as an aircraft wing 10, and more specifically for increasing the flutter speed of an aircraft flying with attached store and reducing the sensitivity of flutter to changes in the pitch inertia and center of gravity location of the store. It comprises soft-spring whereby the store pitch mode is decoupled from support modes and a low frequency active control mechanism which maintains store alignment. In the described embodiment, a pneumatic suspension system 30 both isolates the store 15 in pitch and, under conditions of changing mean load, aligns the store 15 with the wing 10 to which it is attached.